(Reuters) - U.S. cryptocurrency stocks fell in premarket trading on Wednesday after Democratic candidate Kamala Harris put her Republican rival Donald Trump on the defensive in a combative presidential debate.

The former president had positioned himself as a pro-bitcoin candidate whose return could mark a win for the industry that has accused the current administration of regulatory overreach.

Bitcoin, the world's largest cryptocurrency, was down 1.6% on Wednesday, while ether fell 2%.

"The US presidential debate did not address cryptocurrencies directly. However, market sentiment is shifting in favor of Kamala Harris," Valentin Fournier, analyst at research firm BRN.

"This creates a somewhat less optimistic outlook for Bitcoin compared to the more enthusiastic projections made by Trump at the Bitcoin 2024 Conference."

Bets of win for Harris improved to 56% from 53% before the debate, while Trump's chances slipped to 48% from 52%, according to online betting site PredictIt.

Trump had in July courted the crypto industry in a conference in search of donations and votes with a promise of friendlier regulation. "Never sell your bitcoin," Trump said at the time.

In the run-up to the debate, many market participants and analysts viewed bitcoin as the asset to watch for clues on which candidate was gaining an upper hand.

The crypto market is often seen as a risky fringe business with high volatility and has drawn sharp scrutiny from the U.S. Securities and Exchange Commission, which has accused it of flouting securities laws.

But its mainstream appeal has improved a lot, thanks to the support from Wall Street institutions and corporate titans like Elon Musk and the approval of U.S. exchange-traded crypto funds.

Crypto miners Riot Platforms Marathon Digital, and U.S.-listed shares of Hut 8 were down between 2.5% and 3.4% before the bell.

Software firm and BTC buyer MicroStrategy ( MSTR ) fell 4% and crypto exchange Coinbase Global ( COIN ) and Blockchain farm operator Bitfarms were down 2.5% and 3%, respectively.

(Reporting by Manya Saini and Lisa Pauline Mattackal in Bengaluru; Editing by Arun Koyyur)